he will only collapse after using the ms about 3 or 4 times once isnt gonna kill him and he dosent miss i mean he stopped a speeding nail for crying out loud and with the 8 gates guy has done onver 100 matches with kakashi some r pointless but at least some will have a real fight and his greates move is eight gates and kakashi would use sharingan and copy it he knew all about in the chunin exams and he witnessed lee go to 5th gate and looked with his sharingan and im not sure if this was filler or not but he was seen using the first gate during the chunin exams when going up a mountain he also uses the primary lotus which activates the first gate of life and with the chakra that dosent really matter kisames main chakra taxing moves is changing the terrain to make it all water and that big finish he used against guy thats it all the others kakashi can copy like water style shark bomb etcif he makes anything disappear with the MS he'll collapse and get killed , and he can't use the 8 gates cus only guy and lee can do it his body is no where near in physical shape as those 2, and doesn't have the chakra to copy Kisame's attacks and use them